This proposal examines the role of the ras pathway in the development of the zebrafish eye. This includes identifying by homology genes involved in the ras pathway, such as (1) ras (2) rho and (3) drk. Identification of these genes will be followed by localization of their transcripts in the embryonic eye by in situ hybridization. Changes in expression over the course of development will be documented. Dominant negative and dominant positive versions of ras genes will be created and expressed in the embryo. In light of studies demonstrating an antagonistic interaction between the ras pathway and retinoic acid in cell culture, studies will be performed to determine changes in gene expression upon application of exogenous retinoic acid or the retinoic acid inhibitor, citral. These studies have significance in the determination of the axial differences in embryonic development of the eye. As a separate investigation, differential gene display will be attempted to identify genes involved in the retinoic acid response in the developing zebrafish retina.